Building a home Tesla Supercharger (level-3 EV fast charging station)

@yaypie 's Model 3 thread got me thinking about EV charging, and I was wondering--Isn't it possible to create a home charging station capable of the kind of bulk charging that Tesla's 480v superchargers are capable of putting out? They're able to crank out 120KW of power at the plug. I don't see why it couldn't be done.

Most of the conversations I've perused on the Internet seem to be focused on what kind of grid electrical service your residential house is getting from the electric company. Hoping to get 3-phase 480v directly from your grid supplier seems to be where every conversation goes. That...of course...is gonna be a show stopper. Nobody wants to run that kind of cable from the pole to a friggin house.

But that wouldn't be how I'd be doing it anyways. I mean...conceptually...I don't need 480v from the power company. I just need 480v *at the plug*. If I've got a power station in my house...say a bunch of big-ass 2v cells, storing up power all day from solar panels...that comes in as anywhere from 16~22vdc. I can upconvert and downconvert that any way I want. And I only have to support 480v/1kW between the converter and the charging port in the garage. Why don't I see any conversation supporting that kind of strategy?

There's another wrinkle to this, though: the Model 3's built-in charging hardware is only capable of accepting a maximum input current of 48 amps. Superchargers have their own much more expensive charging circuitry and feed DC directly to the battery, bypassing the car's onboard charger.

So if you want to push more than 48 amps, you'll need external charger circuitry of some kind. Tesla's definitely not going to sell this to you, but even for a dedicated DIYer my guess is that the expense of all of this (custom charging hardware, massive batteries, etc.) would be enough that it really wouldn't be worth it unless you've just got money to burn.

Yes, direct to 480v DC was the next logical question for me. :D I mean...if I have the power sitting in a battery bank in my house...it's kinda moronic to have to convert to AC, just to convert it back to DC a few feet away. lol. I figure, though, nobody's going to want to home brew that connection. You want to go from your power bank through a properly engineered converter, and end up with the right ports. If all the available boxes are expecting 3-phase 480AC coming in, well...then upconverting is the way to go, even if it's moronic.

Just spit-balling the sizing, I priced out what a 48v energy storage system would run, hooked up to a fronius controller, and holicow it's about as much as the car. You basically trade the cost of pulling the line (for energy that you have to pay someone for) for the cost of a huge battery bank (that won't last forever). Even on a 30-year payback, it's a pricey initial investment. You really have to figure in the whole residential solar, selling energy back to the grid type of arrangement to make something like this worth it. Setting up something like this just to supply energy to a single car is a losing proposition. Level-2 chargers...a ton more sense for at-home use cases, where most of the time you have the luxury of an overnight charge time.

There’s an experiment going on in Hawaii for basically this concept. The difference is trickle charging the batteries from the grid instead of from solar.

There’s also a few places looking into second life for battery packs pulled from cars because they don’t hold as much charge, or because newer tech has replaced them. One, is using them as s DC fast charge source with renewable trickle charging.

I swear chargepoint used to sell a charger that took in DC. But I can’t find it on their site anymore.

That's pretty much exactly the idea I had in mind. They built it as shared facilities for apartments--multi-tenant places. I had wanted to drop it in a single-family home, powering not only the car but also the house, feeding excesses back to the utility company. It's a pretty standard ambition for a solar house installation. The only twist compared to a regular solar house was increasing the storage capacity & upconverting locally for level-3 charging.

As EVs take off, all this new demand for juice must be forcing towns/cities to evaluate their infrastructure. Remember back in the day, when NYC blackouts would take out huge swaths of the city during the worst of heat waves? No city wants those days back again. They already make developers do the math when permitting large projects (like a when a company moves their headquarters to your town, or developers put in new neighborhoods). Some companies even choose to supplement/replace grid power with things like Bloom boxes. EV demand is going to need to be part of that scrutiny.

I like these designs. They distribute energy gen and storage, keeping it local to the point of demand. That's one way to help make sure infrastructure and demand are balanced, and ultimately help wean us off of dinosaur juice dependency.

Most new residential electrical panels here in my area are 200AMP with 240 Volt supply from PGE, which means max you'll be able to draw 48KW. You'd need much bigger conductors installed from the pole. And most houses only draw a fraction of this, even at peak utilization, so your neighborhood distribution transformer is not sized to take an additional 120KW. I've heard transformers are sized at 4-5KW per house and serve something like 25-50 houses. You're average residential distribution transformer could take just one supercharger, add the load of 50 houses, and you'll blow the transformer. A residential neighborhood is just not wired for that load, so like you mentioned you'll most definitely need to store energy from the grid and/or solar.

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